Low Fuel Pressure

[QuickSpoolSR]

Still trying to get my project car to run right. I got my guages hooked up and realized at idle the fuel pressure was only at about 22psi. I bought a walbro pump and installed it today, when i turn the key to ignition its at 40psi, when i start the car it drops down to around 22-25psi at idle. any ideas? i have a z32 fuel filter too and i have the stock fpr vacum line not t-ed off.

my setup is an an 89 hatch with an sr20det blacktop

[chituntang]

vacuum and/or boost leak?

[cotbu]

Still trying to get my project car to run right. I got my guages hooked up and realized at idle the fuel pressure was only at about 22psi. I bought a walbro pump and installed it today, when i turn the key to ignition its at 40psi, when i start the car it drops down to around 22-25psi at idle. any ideas? i have a z32 fuel filter too and i have the stock fpr vacum line not t-ed off.

my setup is an an 89 hatch with an sr20det blacktop

What kind of vacuum you pulling at idle? What kind of gauge? The oem fpr maybe to weak for your setup. I'm not sure yet, but you maybe a candidate for an adjustable fpr.
What is the pressure with engine on, fpr vacuum removed and line capped/plugged?


vacuum and/or boost leak?
The fpr rises with boost and lower with vacuum, if there is a vacuum leak at idle fuel pressure should be closer to the pump on engine off pressure.

[QuickSpoolSR]

I put on a friends hotpipe and bov setup that i know isnt leaking "i had the turbo xs rfl" and there was no change in fuel pressure, I made sure all hose clamps were on securely, still no change, i took a can of carb cleaner and went crazy spraying anywhere i though there could be a vacuum/boost leak, and didnt hear any change in idle. the fuel pressure is still around 20psi, i also notice that im not building any boost, no matter how i adjust my boost controller, which is manual.

[PoorMans180SX]

Remove the manual boost controller and run a vacuum line straight to the wastegate for now. Let's figure out one problem at a time.

Your FPR is likely bad and leaking pressure past the diaphragm inside.

Pull the vacuum line off the FPR and plug it with your finger. If there is no change in fuel pressure, your FPR is bad.

[jr_ss]

To add to poormans post, if your FPR is bad, upgrade to something adjustable...

[RB240zDET]

Remove the manual boost controller and run a vacuum line straight to the wastegate for now. Let's figure out one problem at a time.

Your FPR is likely bad and leaking pressure past the diaphragm inside.

Pull the vacuum line off the FPR and plug it with your finger. If there is no change in fuel pressure, your FPR is bad.

This is probably the best advice for you situation. And always in the future go with an adjustable FPR.

[QuickSpoolSR]

just put my friends fpr off his running car on mine, no change... hes done like 3 swaps and had several 240's and we are both just stumped. lol im so frustrated iv been working on this car since 09 lol

[PoorMans180SX]

Does the car run bad? Please tell me you've changed the fuel filter.

[QuickSpoolSR]

it sounds like it idles perfectly, yes i have a 300zx fuel filter. it just cuts out when u rev it

[cotbu]

Does the fuel pressure rise when you pinch the return line? I'm sure your lines are connected correctly?! So maybe a faulty gauge? Can you post a video? KOEO and Idle showing vacuum is cool too and what RPM you are idling at?

[QuickSpoolSR]

lol sorry for bumping this old ass thread but today i went out and tried to figure some shit out. I took a multimeter and checked the voltage at the pump and it was only .17 volts coming through the blue/red wire and its supposed to be 12v correct? would it hurt to cut that wire and just wire it directly to the battery with a switch to turn it on, just to see if that will fix the problem?

[Nikeboy355]

If your fuel pressure is low, it is either:

1. Fuel pump bad
2. Fuel injector(s) leaking
3. Fuel pressure regulator bad

To fix:

1. Replace fuel pump, Autozone sells for $89, eBay for $40, Deatchworks is what I run
2. Get fuel injectors services, RC Engineering charges $28.50 for each sidefeed injector
3. Replace fuel pressure regulator, Autozone sells the KA one for $70, eBay has adjustable ones for cheap

But you have already replaced your fuel pump so check the other two...

[QuickSpoolSR]

any info on the low voltage through that wire, isnt it supposed to be 12v. I guess next i will try the injectors, i have a fpr off my friends car that ran fine

[JDMRIDDAZ]

it should be 12v or above...
usually
gets 13.6 when car is running